Electrodeposition of rubber



Patented July 1, 1930 UNITED- STATES 'WILLIAM.ARTHUR WILLIAMS, OFEDINBURGH, SCOTLAND ELECTRODE-POSITION OF RUBBER.

1T0 Drawing. Application filed May 12, 1927, Serial No. 190,965, and inarea Britain March as, 1927.

This invention relates to the electro-deosition of rubber or homologoussubstances rom a vulcanized or unvulcanizedalkaline latex.

In the processes of latex deposition as hitherto carried out, it hasbeen necessary to use a current of sufficient potential to overcome theopposing electro-motive forces of polarization. Otherwise theelectro-motive forces of polarization would act as a suflicient choke tostop the flow of current from the anode to the cathode in the latexsolution, with consequent retardation or stopping of any-rubberdeposition.

This involves the use of an external I effected 0 an aqueous solution ofa metallic salt and an anode is employed of the same metal as that whichis being deposited at the cathode, and that under these conditions thefeeblest current is sufiicient for the reaction. 1 r

I have found that, with such a balanced condition in the presence ofrubber orlike latex, deposition of the rubber takes place at the anodein a homogeneous form free from porosity such as is causedfrom theliberation ofgaseous products. i As an example-of one methodof carryingout the invention, to the. latex is added zinc sulphate in sufficientstrength not to cause coagulation, say, to an ammoniacal latex having analkalinity corresponding approximately to a semi-norsnal solution ofammonia-and a rubber content not exceeding 30% is added zinc sulphatenot exceeding 2%. The electrodes are both of zinc. A weak current notabove that which will electrolyze water, namely, approximately 1.5volts, is sufiicient to cause the necessary reaction, and the rubber isdeposited from the latex free from porosity on that electrode acting asthe anode.

I do IlOtoCOIlfiIlB myself to the materials, chemicals, quantities orpercentages of same 65 herem mentioned, nor to the strength of currentemployed, these being only glven as examples.

It is desirable to change the direction of the current after eachcomplete deposition,

as in the preces's metal is dissolved from the anode and deposited atthe cathode, and by repeatedly reversing the direction of the currentfor each alternate operation, the form of the electrode is maintainedand pitting prevented. The latex can be employed in either itsvulcanized or unvulcanized condition.

Other chemicals or fillers, suchfor example,- as zinc oxide or sulphur,or other vulcanizing agents, with or without accelerators ofvulcanization, whichdo not cause premature coagulation of the latex, maybe added before introducing the electrodes, in order that such chemicalsor fillers will be- ](Some incorporated with the deposited rub- Claims:a

1. A process for the electro-deposition of rubber or homologoussubstances from latex, which consists in the addition to the latex of ametallic salt without effecting coagulation of the latex, and thereaftersubjecting the salt to electrolysis in the presence of an anodeelectrode of the same metal as the salt. a

2. A process for the electro-deposition of rubberor homologoussubstances from latex, which consists in the addition to the latex of ametallic salt without effecting coagulation of the latex, and thereaftersubjecting the solution to electrolysis in the presence of an anodeelectrode of the same metal as the salt, by the use of an externalsource of current of insufficient potential to overcome polarization inthe absence of the metallic salt.

3. A process for the electro-deposition of rubber or homologoussubstances from. latex, which consists in the addition to the latex of ametallic salt without efiecting coagulation of the latex and thereaftersubjecting the solution to electrolysis in the presence of'electrodesboth ofthe same metal as 5 the salt.

4.- A process for the electro-de osition of rubber or homologoussubstances rom'latex, which consists in adding zinc sulphate to thelatex, in insufiicient quantity to effect com agulation, immersing apair of zinc electrodes in the latex, and connecting the electrodes withan external source of a current of a potential not exceeding 1.5 volts.

The fore oing s ecification signed at Edinburgh, cotlan this twentiethday of April, 1927.

WILLIAM ARTHUR WILLIAMS.

